Thimble-equipped insulator



July 13, 1943. R. w. BARNITZ THIMBLE EQUIPPED INSULATOR Filed Sept. 12, 1940 UNITED STATES PATENT OFFICE THIMBLE-EQUIPPED INSULATOR Richard W. Barnitz, Parkersburg, W. Va., assignor to Porcelain Products; Inc., Findlay, Ohio, a corporation of Delaware Application September 12, 1940, Serial No. 356,538

Claims. (Cl. 174-200) The following description relates to a thimbleequipped insulator for high tension electric transmission lines and the thimble itself. Cables for the transmission of high tension electricity are customarily supported on insulators of porcelain or like material which in turn are afiixed to vertical pins or other supports. Electrical porcelain is stifi and unyielding and under abnormal conditions may be fractured. It is, therefore, usual to interpose a thin ductile metal thimble between a modified form of thimble.

the porcelain and the supporting pin. The On the accompanying drawing I have shown thimble is anchored within an axial recess of the the improved device to consist of an insulator insulator and is screw-threaded to receive the p p r 5. This s a e f s e porcelain a d screw-thread of the supporting pin. In normal has characteristics permitting it to be used with operation the thimbl distributes the stresses high tension transmission electric lines. The inand protects the insulator from failure. sulator is supported on a screw-threaded pin 6 The use of such a thimble offers some problems of the usual type.

incidental to assembly and operation. It is not The porcelain insulator has a Vertical longifeasible to produce insulators having axial cavitudinal or axial recess 7 which forms a chamber ties of precise dimensions. Consequently there large enough 0 3 Surround the d Of the is some uncertainty in centering the thimble pin 6. This chamber has a slight taper and the within the axial recess or chamber. It is also walls may b p a n, grooved, sanded or roughened well known that the extended exposed edge of in order to hold a mass of cement 8 without the thimble offers opportunity for the penetradanger of separation. The cement 8 is Portland tion of moisture and deterioration of the cement Cem nt or any other cement suitable -for this which is used. This exposed edge of the thimble where it is sharp or thin may cause corona or radio interference. In the assembly of the customary thimbles an excess amount of cement is forced out of the chamber and into the thimble itself. Again due to the usual variation in sizes the amount of cement used may be insufiicient to completely fill the chamber around the thimble and thus leave a gap at the exposed base edge of its preferred form on the accompanying drawing in which Fig. 1 is a vertical cross-section of an insulator having my improved thimble and mounted on a D Fig. 2 is an enlarged longitudinal cross-section of the improved thimble;

Fig. 3 is a top plan view thereof, and

Fig. 4 is a fragmentary longitudinal section of purpose.

I provide a thimble 9 which is assembled or set within the cement mass 8 while the cement is still plastic. The thimble usually has an internal diameter of 1 to 1% inches. It is made of ductile sheet metal. Zinc is preferred although other equivalent metals may also be used. The sheet is normally approximately one thirty-second of an inch thick. This will permit ready working the thimble and forming, by drawing, die-stamping or rolling. My invention is intended to provide an insulthlmble has a closed top The tapertor in which the thimble in assembl is centered mg slde Wa'n- 15 Corrugated to provlde Splral y thread H which extends both on the outside and without attention. The base edge of the thimble inside surfaces of the tapering side wall. The flares outwardly mto Contact or close fit Wlth the 40 nor screw-thread is adapted to fit over the screwwall of the chamber. It thus effectually seals thread on the pin The Outer groove thread the cement spa pr v ting overflow of the 06- is interrupted as is the usual practice to provide ment penetration moisturesatisfactory anchorage in the cement. In this A further object of my invention s to provide manner the thimble is anchored to the insua rounded, smooth surface for the base flange of later and 111 t be 1oosened by unscrewing the thimble so as to diminish the likelihood of the insulator from the pin. localized electrostatic charges which otherwise The lower portion l2 of the side wall is genmight produce corona or radio interference. erally cylindrical or conical. Its lower edge is A further object of my invention is to materibent out to form a flange or lip l3. ally strengthen the edge of the thimble by dou- Ordinarily the flange 13 will be further bent bling the thickness of the metal at that point. backwardly as indicated in Fig. 2 to provide a Rough handling of the insulator thus is not likely p s s Spaced pa o e s de Wall to cause damage to the porcelain or to the thread l2 of the thi e. e ength o t e p '4 may of th thi bl vary. It may terminate immediately beyond the As an example of my invention I have shown curvature of the flange l3 or alternatively it may be extended substantially. In the latter instance it provides an annular recess which will be of material utility in anchoring the thimble and confining the cement.

I have shown in Fig. 4 the further step by which the lip [4 may be rolled back against the flaring side wall l2. This preserves the flange l3 slightly curved in cross-section and flaring outwardly from the side wall l2. In either case whether the lip i4 is in contact with or parallel to the side wall 12, the same advantages are provided of added strength and freedom from thin, rough edges.

The improved thimble is inserted within the chamber 1 in which the required amount of cement has been placed. The thimble forces the cement around and outwardly from the chamber until it is caught and confined in the annular recess 15. An excess amount of cement will determine the extent to which the lip M will fit into the chamber and in contact with its side wall. A deficiency of cement will leave a small vacant space within the recess Hi. In either event the lip I l or more properly the flange l3 will fit snugly around the side wall of the chamber and seal the latter ofi thus confining the cement and protecting it from penetration of moisture. At the same time the assembly operation necessarily insures proper centering of the thimble.

The provision of a flange greatly improves the appearance of the insulator. At thesame time it minimizes the localization of electrostatic charges and will diminish the possibility of corona discharges.

The added strength of the two thicknesses of the sheet material at the point of contact with the insulator helps materially to strengthen the device. I

While the preferred form of this invention has been described and illustrated it is believed that the invention is capable of embodiment in various forms, proportions and materials so that it is limited solely by the scope of the appended claims.

What I claim is:

1. An electricalinsulator of porcelain or the like, having an axial chamber with a straight inner side wall, a ductile sheet metal thimble spaced within said chamber, and a basal flange on the thimble extending outwardly and backwardly with the peripheral surface of the backwardly extending portion in contact with the straight inner side wall of the chamber.

2. An electrical insulator of porcelain or the like, having an axial chamber with a straight inner side wall, a ductile sheet metal thimble within said chamber, a body of cement in the chamber around the thimble, a basal flange on the thimble extending outwardly toward the said straight inner side wall of said chamber and a reversely directed extension on the flange having extended contact with the said side wall of the chamber.

3. An electrical insulator of porcelain or the like having a tapering axial chamber with a straight inner side wall, a ductile sheet metal thimble within said chamber, said thimble having its walls corrugated to form internal and external screw threaded grooves, a body of cement in the chamber anchoring the thimble to the insulator, a basal flange on the thimble extending outwardly toward the said straight inner side wall of the chamber, and a reversely directed extension on the flange spaced parallel to the side wall of the thimble and confining a portion of said cement mass.

4. An electrical insulator of porcelain or the like having an axial chamber, a ductile sheet metal thimble positioned within said chamber, said thimble having its wall corrugated to form internal and external screw-threaded grooves and having a diameter less than the diameter of said chamber to provide an annular space between said chamber and said thimble, a body of 

